Lighting, along with environment is one of the two most important factors in the way plants grow and develop fruit and flowers. Nutrients do play a vital role but only if lighting and environment are in the appropriate range for the nutrients to take full effect. Artificial light sources pose a variety of potential problems forcing plants to adjust and adapt compromising maximum growth and productivity. It is known that in general, light intensity and light energy are strongly correlated to the level of vegetative growth and if appropriate fruit production, in plants. It is conceivable that a very broad range of the electromagnetic radiation wavelength spectrum may be relevant to growing organisms such as plants. Typically, but not limited as such, the portion of the spectrum that is normally relevant will from ultra-violet (wavelengths of about 10 nm to about 380 nm) through visible light into the infra-red spectrum (wavelengths of about 700 nm to about 1000 nm). Of particular utility, is light in the visible spectrum with wavelengths in the range of about 380 nm to 700 nm.
The greater the level of light intensity and corresponding light energy, then the greater is the amount and/or rate of vegetative growth and possibly fruit production. Light intensity (the amount of light power transferred per unit area) is inversely related to the distance of the plant from the light source squared—meaning that the closer a plant is to its light source, the greater the potential photosynthetic benefit it receives. There is a distance, which varies from plant species to plant species, after which if reduced, plants become saturated by the amount of light energy being received, and any reduction in distance between the plant and its light source ceases to have positive effects on the plant's growth. This point is referred to in the art as the point of light saturation. At a slightly greater distance from said point of saturation however, is the plant's optimal distance from its light source, at which the plant's internodal spacing is minimized, and vegetative growth and fruit production are maximized.
Some facilities for growing plants have the plant growing media/plant containers/plants laid out horizontally, such as in a greenhouse, to capitalize on the use of natural light Use of artificial light sources present problems, with such layouts both horizontal and vertical, not all plants in a group of plants can be placed at an optimal distance from their light sources throughout their entire growth cycle. Plants situated further from the artificial light source may receive exponentially less light than those closer to the light source. Disadvantaged plants can also exhibit negative responses to the light emitted from the light sources, leading for example to curvature defects and decreased vegetative growth in a phenomenon known as “shade avoidance syndrome” (SAS). To minimize the impact of SAS it may require increased inter-nodal spacing between plants.
Some known devices used for growing plants employ moving light apparatuses or rotating apparatuses which may continuously rotate plants relative to their light sources. While these devices may serve to mitigate or “even out” the effects of SAS, they may deprive some plants in the group of plants being grown from receiving optimal light intensity/energy. Such devices may also be power and labor intensive. In horizontal or vertical layouts, maximizing photosynthesis over the entire group of plants can only be achieved through the use of multiple lights to approximate a uniform intensity over the entire layout, further increasing power requirements and possibly requiring cooling systems to be utilized. Furthermore, light sources in horizontal layouts typically fail to function at peak efficiency, releasing radiation in all directions due to the phenomenon of “scattering.”
To attempt to provide optimal photo-synthetically active radiation (PAR) that reaches all plants in a group of plants, and to try to save the amount of power consumed and the cost of labor incurred, more efficient/effective ways of growing plants are desirable.
Canadian Patent Document 2,343,254 discloses a rotating drum mounted on a base in such a way as to enable the rotation of said drum around a light source positioned at the rotational axis of said drum. The surface of the drum contains holes for plant pots to be placed in, in such a way that the plants grow radially inwardly from the drum circumference and toward the central light source. The radial distribution of the plants ensures may provide a relatively more even distribution of light intensity to the plants held in the device without extra lighting being required, alleviating SAS and ensuring a generally consistent PAR level for the plants. Light previously lost to the “scatter” phenomenon is substantially directed to plant pots positioned radially around the light source. Substantial energy costs may be also alleviated, because using a motor to drive a rotary device may reduce overall energy requirements. The rotation of the plants has the added benefit that the positive phototrophic responses and negative responses associated with gravity of the plants can be mitigated, and may result in a further increase in vegetative growth without any corresponding increase in required labor. Light previously lost to the “scatter” phenomenon may become photo-synthetically active radiation, reaching plants positioned all around the light source. During rotation, the plant pots may also pass through a reservoir containing water and a nutrient solution located at the base of the rotary device, watering the occupants once per rotation.
However, the apparatus disclosed in Canadian Patent 2,343,254 has some disadvantages. The inflexible drum allows for an even distribution of light to all plants, but the distribution occurs at a fixed intensity. Without being able to vary the distance between the plants and the light source, light intensity can only be optimal for specific plants, or plants at specific stages of growth. A further disadvantage results from the nutrient reservoir as a watering means. After the plants and plants growing medium have passed through the reservoir, they often drip on the light source, having become oversaturated by liquid. In addition to the maintenance problems caused by said dripping, the oversaturation of the medium is often not optimal for the plant's growth, and the excess liquid content can encourage the propagation of harmful molds and fungi.
To enable variations in the light intensity experienced by the plants within the apparatus, Canadian patent 2,460,465 discloses an apparatus which employs a variable diameter ring comprised of separate interlocking ring segments assembled exteriorly of the laterally running medium retaining members. By using an external ring instead of a static cylindrical or drum shape, ring segments may be added or removed to cause variations in the diameter of said cylinder according to the needs of the plants at a specific growth stage. In this way some limited variations in the proximity of the plants to the light source can be achieved. Also, instead of a reservoir, Canadian patent 2,460,465 discloses an injection based watering system located exteriorly of the ring and medium retaining members, allowing for the timed release of water and nutrients to said members.
However Canadian patent 2,460,465 also has some shortcomings. Modifications made to the medium retaining members affect all the medium retaining members at the same time. The calculation of optimal light intensity made by the grower will typically be an average of the plants in all of the medium retaining members. Further inconvenience may result from the addition and subtraction of ring segments that is necessary in order to make significant adjustments to the diameter at which the medium retaining members are held. As the plants within the apparatus grow, the diameter may be increased by the addition of ring segments and medium retaining members. However, medium retaining members must either be empty or must contain plants already at the optimal growth stage to benefit from addition to the apparatus. This presupposes the growth of said plants being undertaken elsewhere, such as other rotary devices of varying scales. Like other rotary devices in the prior art, a number of devices built on varying scales are required for optimal light intensity across an entire yield throughout the plants' entire growth cycles. The distance of the plants can only be stepped at discrete changes thus it does nothing to optimize light at all times.
A further inconvenience arises from the fact that the ring shape itself should be comprised of at least about eight segments to be substantially circular. Any decrease in the number of segments from the cylindrical layout formed by the medium retaining members becomes increasingly polygonal in shape, causing exponential differences in intensity experienced by those plants further from the light source, and reintroducing the symptoms of SAS as described above.
Another inconvenience results from the immobility of the watering system. A plurality of liquid injectors extends from a main liquid distribution member, which is in turn attached to a water source. Because each injector does not have its own unique liquid input port, each distribution member must have a predetermined and unchangeable number of injectors attached. A further problem arises from the immobility of the watering element. Because the element is unable to advance or retreat along a predetermined path to penetrate or exit the medium retaining member, the injection designed to obviate dripping is less than optimal.
Accordingly, an improved rotary plant growing apparatus is desirable. It is desirable to provide a rotary plant growing device capable of providing substantially optimal light intensity for the plants throughout their entire life cycles, while at the same time attempting to reduce at least some of the most significant problems in known rotary devices. These problems include, but are not limited to: cumbersome, problematic, imprecise or non-existent light intensity modifiability and; dripping of liquid on the central light source. It is desirable to provide rotary devices which: provide a more consistent light intensity distribution over the entire group of plants; obviate or at least reduce shade avoidance syndrome and its symptoms; and provide improved vegetative growth/fruit yield production; and be more energy efficient.